Matrix clock



FIG. 1 is a front elevational view of a matrix clock showing our new design in use in an environment;

FIG. 2 is a front elevational view thereof in use in an alternate environment;

FIG. 3 is a front elevational view thereof in use in a second alternate environment; and,

FIG. 4 is a front elevational view thereof in use in a third alternate environment.

The computer monitor in FIG. 1, the laptop in FIG. 2, the mobile phone in FIG. 3, and the wristwatch in FIG. 4 have been shown for the purpose of illustrating environment that forms no part of the claimed design. 

CLAIM The ornamental design for a matrix clock, as shown and described. 